This abstract reminded me of Laura Periman and Cindy Matossian’s talks on cosmetic matters during ASCRS last May. They both mentioned the importance of eyelash length - that there really is an optimal length of lashes, and that messing with your eyelashes can actually make dry eye worse by essentially funneling air onto your eyes. Fascinating.

So anyway, I ran across this study and as you can see, one particular phrase leaped out….

How eyelashes can protect the eye through inhibiting ocular water evaporation: a chemical engineering perspective. Zou S, Zha J, Xiao J, Chen XD. J R Soc Interface. 2019 Oct 31;16(159):20190425.

Bionics is a fascinating subject that has inspired many inventions through learning from biological structures and functions. In this work, a coupled multi-physics model has been developed to characterize ocular water evaporation with realistic eyelash structures taken into account. From a chemical engineering perspective, the protective function of human eyelashes in terms of evaporation inhibition has been rationally revealed. Systematic investigations were carried out to elucidate the effects of different eyelash lengths, orientations and inlet air directions on water evaporation on the ocular surface. The results clearly demonstrate that regardless of inlet air directions and eyelash orientations, increasing eyelash length from zero to an optimal length can effectively reduce water evaporation. However, further increase in the eyelash length can lead to enhanced evaporation. For the normal and parallel inlet air directions, the optimal eyelash length is around 15-30% of the eye width and can offer approximately 10-30% evaporation reduction when compared with the cases without eyelashes. These values are independent of the eyelash orientation. This investigation provides valuable data for in-depth understanding of the protective function of the eyelashes, which can be used in the future to improve and optimize bionic designs inspired by human eyelashes.